Strand unreeling device with automatic tension control

ABSTRACT

In a device for unreeling a uniformly and automatically tensioned strand from a non-rotatably held bobbin, there are provided an unreeling arm caused to orbit about said bobbin by the force exerted by a strand pulling apparatus, a braking mechanism to dampen the rotation of said unreeling arm and a brake control or balancing mechanism to which there are applied a predetermined braking force and the force exerted by said strand pulling apparatus. The result of these two counteracting forces controls the braking effect on said unreeling arm.

United States Patent Bonnabaud et al.

[151 3,655,108 [45] Apr. 11,1972

[54] STRAND UNREELING DEVICE WITH AUTOMATIC TENSION CONTROL [72] Inventors: Joannes Francis Marcel Bonnabaud, 23, Rue Noelas 42, Roanne; Claude Brat, 119 Rue du Marechal Foch 42, Riorges, both of France 22 Filed: Nov. 14, 1969 21 Appl.No.: 876,912

[30] Foreign Application Priority Data Nov. 14, 1968 France ..l73652 [52] US. Cl ..242/128 [51] Int. Cl ..B65h 49/00 [58] Field ofSearch ..242/128.129.1295-1298 [56] References Cited UNITED STATES PATENTS 1,873,422 8/1932 Keller ..242/128 FOREIGN PATENTS OR APPLICATIONS 1,017,904 l/l966 Great Britain ..242/128 Primary Examiner--Leonard D. Christian Attorney--Edwin E. Greigg 57 I ABSTRACT In a device for unreeling a uniformly and automatically tensioned strand from a non-rotatably held bobbin, there are provided an unreeling arm caused to orbit about said bobbin by the force exerted by a strand pulling apparatus, a braking mechanism to dampen the rotation of said unreeling arm and a brake control or balancing mechanism to which there are applied a predetermined braking force and the force exerted by said strand pulling apparatus. The result of these two counteracting forces controls the braking effect on said unreeling arm.

7 Claims, 4 Drawing Figures Patented A ril 11, 1972 3,655,108

2 Sheets-Sheet l Patented A ril 11, 1972 3,655,108

2 Shoots-Sheet 2 BACKGROUND OF THE INVENTION This invention relates to a device by means of which a strand, such as a thread, filament or the like is maintained under automatically regulated tension as it is unreeled from a bobbin with the application of a remote, continuous pulling force.

For the aforenoted purpose devices have been used wherein the strand, running from a rotating bobbin, passes over a wheel provided with a braking device and is then trained I about a pulley so that two horizontal strand flights are obtained. The pulley is subjected to a constant horizontal force opposed to that exerted on the pulley by the two strand flights and is adapted to shift horizontally as the tension on the two strand flights varies. Said shift modifies the braking force exerted on the wheel and thus adjusts the tension to a value required to balance the said constant horizontal force.

In known devices of the aforenoted type the strand is not subjected to a uniform tension along its entire length. In fact, the strand portion extending from the bobbin to the braking wheel has a tension which is notably lower than that of the horizontal strand flight extending from the wheel to the pulley. This difference of tension is necessary to impart on the wheel a torque which is at least equal to the braking torque. Thus, the strand portion upstream of the wheel is liable to buckle and, in case the bobbin is disposed vertically, the strand layers thereon are likely to slip.

It is another disadvantage of a device of the aforenoted type that the tension in the last named portion of the strand is of a haphazard nature and, further, each change of this tension causes the operation of an adjusting mechanism. Also, a device of the aforenoted type is not adapted to high speed, low tension unreeling, since the inertia of the bobbin has to be overcome.

Furthermore, since the bobbin itself is not braked, it has the tendency of unreeling by inertia. Thus, in case of a sudden drop of tension caused, for example, by an abrupt stoppage of the pulling mechanism, loops and twists may be formed in the strand.

OBJECT AND SUMMARY OF THE INVENTION It is a primary object of the invention to provide an improved device of the aforenoted type from which the disadvantages outlined above are eliminated.

Briefly stated, according to the invention, the unreeling device comprises an unreeling arm orbiting about a stationary bobbin and engaging the strand extending therefrom. The rotary motion of the arm which is caused by a strand pulling apparatus externally of the unreeling device, is dampened by a braking mechanism. The strand extending from said arm is trained about a pulley which is displaceable parallel to its own axis. The pulling force exerted by said strand pulling apparatus is counteracted by a weight exerting a force on said displaceable pulley. The variation of said pulling force causes a displacement of said pulley and the braking force exerted by said braking mechanism on said unreeling arm is varied by means responsive to the displacement of said pulley.

In this manner, a constant tension of the entire running length of the strand is ensured; said tension is determined by the force exerted by said weight.

The invention will be better understood, as well as further objects and advantages will become more apparent from the ensuing detailed specification of a preferred, although exemplary embodiment taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side elevational view, partially in section, of a preferred embodiment of the invention;

FIG. 2 is a detailed sectional view taken along line II-Il of FIG. 1;

FIG. 3 is a schematic isometric view of a modification of one part of the preferred embodiment and FIG. 4 is a schematic side elevational view, partially in section of a modification of the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIG. 1, there is shown a bobbin 1 secured, by means of a bolt 2, in an axially vertical position to a support S forming part of a frame B.

Above the bobbin 1, spaced therefrom and in axial alignment therewith, there is rotatably mounted in a horizontal extension C of frame B, a joumalling member 4, carrying at its upper terminus an integral disc D.

To the joumalling member 4 there is fixedly secured the upper terminus of an unreeling arm generally indicated at 5. The lower terminus of the latter rotatably surrounds, by suitable bearing means, a cylindrical neck portion 3 which forms part of support 8 and which is disposed in axial alignment with the bobbin 1. The unreeling arm 5 is formed of an upper portion S extending downward from joumalling member 4 in an inclined manner, a vertical mid-portion M spaced from bobbin 1 and a horizontal lower portion I terminating at the cylindrical neck portion 3 of support S.

The assembly 4, 5 may thus rotate about the axis of the bobbin 1.

On the joumalling member 4 there is mounted a roller 6 in such a manner that its groove base is substantially tangent to the axis of rotation of assembly 4, 5. The unreeling arm 5 carries a roller 7 which guides the strand (generally indicated at F) from bobbin 1 to roller 6 clear of either the bobbin 1 or the arm 5. The joumalling member 4 is provided with an axial bore T through which the strand F passes and extends upwardly.

Any traction exerted on the strand would cause the arm 5 to orbit about bobbin 1 and would ensure an unreeling operation without any tension other than that caused by the dampening of the free rotation of the arm due solely to bearing friction and air resistance. For tensioning the strand running from the bobbin 1, it is thus sufiicient to brake to a greater or lesser extent the rotating assembly. Such a braking is effected by means of a tension compensator or balancing mechanism mounted on the frame B and now to be described.

On frame B there is mounted a pulley 8, the groove base of which is substantially tangent to the axis of the unreeling assembly 4, 5. The pulley 8 guides the strand, as indicated at 12, towards another pulley 9 mounted on a mobile carriage 10 suspended from a horizontal bar 14. The strand is trained about pulley 9 through an angle of approximately and is directed thereafter, as indicated at 13, horizontally towards a pulley 11, the rotational plane of which is variable. From pulley 11 the strand proceeds to a pulling apparatus, now shown.

A weighted slide 15 is displaceably suspended on a bar pivotable in a vertical plane about pin 17 affixed to frame B. The slide 15 is connected to carriage 10, so that these two components are constrained to move in unison along bars 14 and 16, respectively.

The displacement of carriage 10 on bar 14 is limited by spaced abutments 22 and 23.

Turning now to FIG. 2, to the bar 16 there is keyed a horizontally offstanding small arm 18 through which the bar 16 bears on a brake shoe 19 cooperating with the upper face of disc D of the rotary unreeling mechanism. An adjusting screw 20 provides for the horizontal adjustment of the bar 16.

The braking force exerted by the brake shoe 19 on the disc D dampens the rotation of the unreeling assembly 4,5 and depends on the downward directed force of the bar 16 at the location of engagement with brake shoe 19. The last-named force, in turn, is determined by the position of weighted slide 15 on bar 16. The farther away the slide 15 is from pivot pin 17, the greater the clockwise torque thereabout and the greater the downward force on bar 16.

A counterweight 21 (FIG. 1) is secured to an end of bar 16 and opposes the aforenoted torque on pivot pin 17 to such an extent that in case carriage 10 is in engagement with abutment 22, the pressure on the brake shoe 19 is negligible.

To the carriage 10 there is attached a line 24 which extends horizontally towards a pulley 25, is trained thereabout and continues downward in a vertical direction. To the free end of line 24 there is attached a mass 26, the total weight of which is twice the desired tension of the running strand.

IN order to maintain the friction forces on the moving components at a lowest possible level, the carriage 10, the slide 15 and all pulleys hereinbefore mentioned are preferably supported by ball bearing or roller bearing means.

It is seen that, apart from friction or deforrnational effects, the tension in the strand flights 12 and 13 is half of the force applied to line 24 by the mass 26, provided the carriage 10 is not in engagement with either abutment 22 or 23. Since none of the guide rollers is braked and no braking action is imparted directly on the strand, the aforenoted tension is uniform in each point of the running length of the strand from the bobbin 1 to the drawing apparatus disposed downstream of pulley 11.

OPERATION OF THE PREFERRED EMBODIMENT If, during the unreeling operation, the tension of the strand tends to increase and exceeds half the weight of mass 26, the equilibrium of foreces exerted on carriage 10 is disturbed and, as a result, the carriage 10, together with slide 15, displaced towards the left. As the weighted slide 15 approaches the horizontal pivot pin 17, the torque thereabout decreases and, consequently, the pressure of the brake shoe 19 on surface D also decreases. Thus, the orbital motion of the unreeling arm 5 is less dampened and, as a result, the tension of the strand is reduced.

On the other hand, if the strand tension tends to fall below half the weight of mass 26, the contrary result is obtained: the slide 15 moved by the carriage 10 is displaced towards the right and the moment about the pin 17 increases, whereby the pressure of the shoe 19 and thus the braking force on the unreeling arm 5 also increases.

A sudden removal of tension from the strand, caused, for example, by an abrupt stoppage of the strand pulling mechanism, would normally permit a continued orbital unreeling movement of arm 5 due to inertia, allowing carriage 10 to engage abutment 23 rendering the tension control ineffective. In order to avoid such an undesirable result, in the range of the right hand termmal portion of the travelling path of slide 15, there is provided a weighted cam track 26a pivotally attached to frame B by a pin 27 and maintained in a substantially horizontal position of rest by an abutment 28 also affixed to frame B. Should the carriage l and the slide 15 shift to the far right in response to a substantial slackening of the strand, small roller 30 carried by slide 15 will be forced to travel in engagement with the lower camming face of cam track 26a. Thus, a positive, downwardly directed clamping force is exerted on slide 15, increasing progressively and very substantially the clockwise torque about pivot pin 17. As a result, the unreeling arm is subjected to a strong, energetic braking action.

Instead of substantially increasing the weight of mass 26 in case a high constant tension in the strand is desired (which would lead to a regulation with the carriage continuously in the vicinity of abutment 23), an auxiliary brake shoe 31 is provided (FIG. 2). Its pressure on the disc D may be varied by adjusting a screw 32 to provide a permanent supplementary braking etTect. Thus, even for high strand tensions, the carriage may assume a position substantially medially with respect to the abutment 22 and 23.

The apparatus described hereinabove thus permits, by means of an arrangement characterized by a horizontal displacement of a compensator creating a variable braking torque, a correction of the strand tension and a maintenance thereof at a uniform value along the entire running length. At the same time, the device indicates the tension without ambiguity by means of the known weight values of a mass applied. This feature is particularly advantageous in case the unreeling operation is a first step of an assembly operation.

Because of the numerical indication of the tension applied, it may be ensured in a simple manner that all individual unreeling devices operate with the same tension so that a well balanced assembling operation is obtained.

By means of the afore-described apparatus very high unreeling speeds may be achieved due to the fact that the bobbin itself is stationary, the light-weight rotating parts have a small inertia and the braking effect may be reduced to a zero value. Also, an abrupt stoppage of a strand pulling apparatus is possible even from high speeds without risking a slackening of the strand.

The fact that a permanent tension is exerted on the strand along its entire running length is also advantageous in that no loops or twists may be formed and the strand layers may not slide on the bobbin despite its vertical arrangement as shown in the embodiment according to FIG. 1.

MODIFICATIONS OF THE PREFERRED EMBODIMENT If the distance between the two radial terminal flanges of the bobbin 1 is large with respect to the bobbin diameter or, if it is essential that the strand be drawn orthogonally with respect to the bobbin axis, the unreeling arm 5 may be complemented by an elongated rotary roll 33 (FIG. 3) disposed parallel to the bobbin 1 and mounted on a lateral, arm-like extension 34 integral with unreeling arm 5. The strand, prior to be engaged by the roller 7, is trained about the roll 33.

The embodiment shown in FIG. 1 has a structure particularly adapted to unreel a bobbin disposed vertically. Often, however, a horizontal or oblique positioning of the bobbin is more advantageous, particularly if the winding thereon is too soft. If such bobbin is held vertically for unreeling, there is a risk of downward slippage of the windings.

A modified exemplary structure of a device for unreeling a horizontally held bobbin is depicted in FIG. 4.

At the outset it is noted that in case of a non-vertical disposition of the bobbin, means have to be provided to balance the rotating assembly. This is particularly the case for bobbins having dimensions which reqUire the use of an intermediate roller (such as roll 33 shown in FIG. 3). The incorporation of balancing features contributes to a significant increase in the inertia of the rotating assembly. The resistance of air to high rotary speeds increases to such an extent that a system which would be limited only to brake the unreeling mechanism would be insufficient since, in some cases, the said mechanism is already braked to an eccessive extent by diverse mechanical frictions and by the resistance of air.

It follows from the foregoing that under certain circumstances the unreeling operation-while maintaining the desired strand tensionhas to be assisted and not braked. To this end the modified structure shown in FIG. 4 is provided.

The principle of the automatic control proper is the same as in the precedingly described embodiment. The effect of counterweight 21, however, is different. While in the device according to FIG. 1, the bar 16 is balanced when the carriage 10 is in engagement with abutment 22, according to the embodiment described in FIG. 4, such balancing of the bar 16 occurs when the carriage 10 is disposed substantially in the mid-portion of its possible course.

A lever 35 integral with bar 16 and extending at an angle therefrom, controls the axial displacement of a sleeve 36 constrained to rotate as a unit with part 37 which carries the unreeling elements.

If the tension of the strand decreases and, as a result, the carriage 10 is displaced from its aforenoted position of equilibrium towards the abutment 23, the brake control is effected, as decribed before, by a variable pressure on the brake shoe 38 which has the same function as the brake shoe 19 incorporated in the embodiment shown in FIG. 1. Stated in different terms, the closer carriage 10 moves to abutment 23, the greater will be the braking torque transmitted through brake shoe 38 to sleeve 36 and thus to part 37.

If, on the other hand, the tension of the strand increases and the carriage is shifted from its position of equilibrium towards the abutment 22, the lever 35 exerts a force in the direction of arrow 40 carrying the sleeve 36 into contact with a clutch element 39 continuously rotated by a motor 43 in the same sense as part 37 and with a speed at least equal to the required unreeling speed of part 37. Thus, the part 37, through friction element 41 and sleeve 36, is driven by motor 43 with a slippage which decreases with increasing pressure. Stated in different terms, the closer carriage 10 moves to abutment 22, the greater will be the aiding torque transmitted from motor 43 to rotating part 37.

The sleeve 36 may thus shift in response to the displacements of the weighted slide in order to permit either an activation of the brake shoe 38 or the activation of the driving clutch element 39 in order to obtain in the strand a constant and uniform predetermined tension along its entire running length.

it is thus seen that by virtue of the structure shown in FIG. 4, an effective tension control may be effected even if the built in resistances tend to give rise to a tension which would be in excess of the strand tension sought.

The structure according to FIG. 4 is adapted for a dual feed: the shaft 42 may serve as a support for a reserve bobbin.

Further, a complemental loading device for heavy bobbins may be attached, if necessary.

What is claimed is:

l. A device for unreeling a strand under predetermined tension from a bobbin comprising:

A. support means for non-rotatably holding said bobbin,

B. an unreeling arm assembly rotatable substantially axially about said bobbin and including means orbiting about said bobbin and engaging said strand and unreeling the same from said bobbin, said unreeling arm assembly rotatable by a pulling force exerted on said strand,

C. a controllable braking mechanism associated with said unreeling arm assembly to dampen the latter in its rotation and D. a balancing mechanism exposed to a first and a second force, said first force formed of a predetermined constant force, said second force opposing said first force and constituted by said pulling force, said balancing mechanism including 1. a pulley about which the running strand is trained downstream of said unreeling arm assembly,

2. carriage means supporting said pulley and displaceable in the direction and under the effect of both said first and second forces and 3. a force generating means operatively connected to said carriage means and to said braking mechanism for exerting a force to the latter as a function of the position of said carriage means, said force generating means including a. a bar pivotable in a substantially vertical plane about a pin and connected to said braking mechanism and b. a sliding member suspended from said bar and displaceable thereon in unison with said carriage means, said sliding member exerts a torque on said bar about said pin, said bar exerts a force on said braking mechanism in response to said torque.

2. A device as defined in claim 1, including a cam track disposed in the path of travel of said sliding member, said sliding member engages said cam track when said second force has fallen substantially below said first force, said cam track, when in engagement with said sliding member, exerts a force thereon that aids said torque.

3. A device as defined in claim 2, wherein said cam track is weighted and pivotally held.

4. A device for unreeling a strand under predetermined tension from a bobbin comprising:

A. support means for non-rotatably holding said bobbin, B. an unreeling arm assembly rotatable substantially axially about said bobbin and including means orbitin about said bobbin and engaging said s rand and unree ing the same from said bobbin, said unreeling arm assembly rotatable by a pulling force exerted on said strand,

C. a controllable braking mechanism associated with said unreeling arm assembly to dampen the latter in its rotation and D. a balancing mechanism exposed to a first and a second force, said first force formed of a predetermined constant force constituted by the weight of a mass, said second force opposing said first force and constituted by said pulling force, said balancing mechanism including 1. a pulley about which the running strand is trained downstream of said unreeling arm assembly,

2. carriage means supporting said pulley and displaceable in the direction and under the effect of both said first and second forces, said mass being attached to said carriage means and 3. a force generating means operatively connected to said carriage means and to said braking mechanism for exerting a force to the latter as a function of the position of said carriage means.

5. A devicefor unreeling a strand under predetermined tension from a bobbin comprising:

A. support means for non-rotatably holding said bobbin,

B. an unreeling arm assembly rotatable substantially axially about said bobbin and including means orbiting about said bobbin and engaging said strand and unreeling the same from said bobbin, said unreeling arm assembly rotatable by a pulling force exerted on said strand,

C. a controllable braking mechanism associated with said unreeling arm assembly to dampen the latter in its rotation,

D. a balancing mechanism exposed to a first and a second force, said first force formed of a predetermined constant force, said second force opposing said first force and constituted by said pulling force, said balancing mechanism including transmission means for imparting a force, responsive to the resultant of said first and second forces, to said braking mechanism to dampen the rotation of said unreeling arm assembly in response to said resultant and i E. motor means aiding the rotation of said unreeling arm assembly, said motor means becoming operative when said second force exceeds said first force and, at the same time, the frictionalforces inherent in said device dampen the rotation of said unreeling arm assembly to an extent causing a greater than desired tension in the running length of said strand.

6. A device as defined in claim 5, wherein said support means holds said bobbin in an axially horizontal position.

7. A device as defined in claim 5, including A. a motor,

B. a clutch member mounted on said unreeling arm assembly coaxially therewith and freely rotatably with respect thereto, said clutch member is continuously driven by said motor and C. a sleeve member mounted adjacent said clutch member on said unreeling arm assembly coaxially therewith and axially slidable thereto, but constrained to rotate in unison therewith, said sleeve member is operatively connected to said balancing mechanism and is urged thereby into contact with a stationary brake shoe for dampening the rotation of said unreeling arm assembly when said first force exceeds said second force, said sleeve member is urged by said balancing mechanism into contact with said continuously driven clutch member for transmitting an aiding torque to said unreeling arm assembly when said second force exceeds said first force. 

1. A device for unreeling a strand under predetermined tension from a bobbin comprising: A. support means for non-rotatably holding said bobbin, B. an unreeling arm assembly rotatable substantially axially about said bobbin and including means orbiting about said bobbin and engaging said strand and unreeling the same from said bobbin, said unreeling arm assembly rotatable by a pulling force exerted on said strand, C. a controllable braking mechanism associated with said unreeling arm assembly to dampen the latter in its rotation and D. a balancing mechanism exposed to a first and a second force, said first force formed of a predetermined constant force, said second force opposing said first force and constituted by said pulling force, said balancing mechanism including
 1. a pulley about which the running strand is trained downstream of said unreeling arm assembly,
 2. carriage means supporting said pulley and displaceable in the direction and under the effect of both said first and second forces and
 3. a force generating means operatively connected to said carriage means and to said braking mechanism for exerting a force to the latter as a function of the position of said carriage means, said force genErating means including a. a bar pivotable in a substantially vertical plane about a pin and connected to said braking mechanism and b. a sliding member suspended from said bar and displaceable thereon in unison with said carriage means, said sliding member exerts a torque on said bar about said pin, said bar exerts a force on said braking mechanism in response to said torque.
 2. carriage means supporting said pulley and displaceable in the direction and under the effect of both said first and second forces and
 2. A device as defined in claim 1, including a cam track disposed in the path of travel of said sliding member, said sliding member engages said cam track when said second force has fallen substantially below said first force, said cam track, when in engagement with said sliding member, exerts a force thereon that aids said torque.
 2. carriage means supporting said pulley and displaceable in the direction and under the effect of both said first and second forces, said mass being attached to said carriage means and
 3. a force generating means operatively connected to said carriage means and to said braking mechanism for exerting a force to the latter as a function of the position of said carriage means.
 3. A device as defined in claim 2, wherein said cam track is weighted and pivotally held.
 3. a force generating means operatively connected to said carriage means and to said braking mechanism for exerting a force to the latter as a function of the position of said carriage means, said force genErating means including a. a bar pivotable in a substantially vertical plane about a pin and connected to said braking mechanism and b. a sliding member suspended from said bar and displaceable thereon in unison with said carriage means, said sliding member exerts a torque on said bar about said pin, said bar exerts a force on said braking mechanism in response to said torque.
 4. A device for unreeling a strand under predetermined tension from a bobbin comprising: A. support means for non-rotatably holding said bobbin, B. an unreeling arm assembly rotatable substantially axially about said bobbin and including means orbiting about said bobbin and engaging said strand and unreeling the same from said bobbin, said unreeling arm assembly rotatable by a pulling force exerted on said strand, C. a controllable braking mechanism associated with said unreeling arm assembly to dampen the latter in its rotation and D. a balancing mechanism exposed to a first and a second force, said first force formed of a predetermined constant force constituted by the weight of a mass, said second force opposing said first force and constituted by said pulling force, said balancing mechanism including
 5. A device for unreeling a strand under predetermined tension from a bobbin comprising: A. support means for non-rotatably holding said bobbin, B. an unreeling arm assembly rotatable substantially axially about said bobbin and including means orbiting about said bobbin and engaging said strand and unreeling the same from said bobbin, said unreeling arm assembly rotatable by a pulling force exerted on said strand, C. a controllable braking mechanism associated with said unreeling arm assembly to dampen the latter in its rotation, D. a balancing mechanism exposed to a first and a second force, said first force formed of a predetermined constant force, said second force opposing said first force and constituted by said pulling force, said balancing mechanism including transmission means for imparting a force, responsive to the resultant of said first and second forces, to said braking mechanism to dampen the rotation of said unreeling arm assembly in response to said resultant and E. motor means aiding the rotation of said unreeling arm assembly, said motor means becoming operative when said second force exceeds said first force and, at the same time, the frictional forces inherent in said device dampen the rotation of said unreeling arm assembly to an extent causing a greater than desired tension in the running length of said strand.
 6. A device as defined in claim 5, wherein said support means holds said bobbin in an axially horizontal position.
 7. A device as defined in claim 5, including A. a motor, B. a clutch member mounted on said unreeling arm assembly coaxially therewith and freely rotatably with respect thereto, said clutch member is continuously driven by said motor and C. a sleeve member mounted adjacent said clutch member on said unreeling arm assembly coaxially therewith and axially sLidable thereto, but constrained to rotate in unison therewith, said sleeve member is operatively connected to said balancing mechanism and is urged thereby into contact with a stationary brake shoe for dampening the rotation of said unreeling arm assembly when said first force exceeds said second force, said sleeve member is urged by said balancing mechanism into contact with said continuously driven clutch member for transmitting an aiding torque to said unreeling arm assembly when said second force exceeds said first force. 